THE SCHOOL OF THE SHORE 41 



wafting minute creatures and nutritive parti- 

 cles into its mouth. Professor Huxley com- 

 pared the acorn-shell to a shrimp fixed head- 

 downwards, and kicking its food into its 

 mouth with its legs. But it is a peculiarly 

 graceful kind of kicking! Many of them must 

 expend much energy before they sift out a 

 meal from the clear water. They live in cas- 

 tles ; but not castles of indolence. The acorn- 

 shells are relatives and probably descendants 

 of the stalked barnacles which fix themselves 

 to wooden ships and floating logs. Like these 

 they are free-swimming in their early youth; 

 but they fix themselves eventually by their 

 feelers and settle down. A rampart of lime 

 is formed round about, and the animal is 

 cemented down for the rest of its life. Not a 

 very exciting life, perhaps, but a very safe 

 one, for no waves are strong enough to wash 

 the barnacle from its rock. Sea-urchins have 

 meals of barnacle when they are tired of sea- 

 weeds, and dog-whelks also browse on them; 

 but they hold their own well. Their eggs are 

 washed out by the tide and hatch in the open 

 water, and there we also find the transparent 

 feather-like moults of the adults which have 

 been cast in the pools. 



